Due to their excellent properties and good melt-moldability, crystalline polyamides such as nylon 6 and nylon 66 have been widely used in fibers for clothing and industrial materials and as general-purpose engineering plastics.
However, it has been noted that such crystalline polyamides have disadvantages such as insufficient heat resistance and poor dimensional stability due to absorption of water. Particularly, in the field of electrical and electronic devices that require reflow soldering heat resistance with the recent development of surface mount technology (SMT) and in automobile components such as engine room components that increasingly require higher heat resistance, conventional polyamides have become practically useless, and there is a growing demand for polyamides having better heat resistance, dimensional stability, mechanical properties, and physicochemical properties.
To meet these demands, there have been proposed various polyamides including an aromatic dicarboxylic acid unit (so-called “semi-aromatic polyamides”), such as modified PA6-T and PA9-T, having better heat resistance and chemical resistance than conventional aliphatic polyamides such as polyamide 6 and polyamide 66 (see Patent Literatures 1 and 2).